Apparatus for drying damp web material

ABSTRACT

Apparatus for drying damp web material having a distribution chamber with inlet and outlet slots through which the material is moved, the chamber having means for receiving compressed gas to which the material is subjected for uniform drying.

United States Patent 1 Lefebvre et al.

[ May 28, 1974 APPARATUS FOR DRYING DAMP WEB MATERIAL Inventors: MichelS. M. Letebvre; Philippe D.

Lapierre, both of Saint-Quentin, France Omnium de Prospectivelndustrielle S.A., Neuville Saint-Amand, France Filed: Jan. 24, 1973Appl. N0.: 326,427

Assignee:

US. Cl. 34/155, 34/156 Int. Cl. F26b 13/00 Field of Search 34/155, 51,54, 156, 151,

References Cited UNITED STATES PATENTS 7/1963 Morrison et al. 34/68 Eigeet al 34/54 Brown 34/156 Daane 34/122 Sutherland et al 34/54 Goodman etal.. 34/155 Daane 34/155 Hamilton et al 34/54 Primary Examinerl(ennethW. Sprague Assistant ExaminerLarry I. Schwartz Attorney, Agent, orFirm-Lewis H. Eslinger, Esq.; Alvin Sinderbrand, Esq.

Apparatus for drying damp web material having a dis- ABSTRACT tributionchamber with inlet and outlet slots through which the material is moved,the chamber having means for receiving compressed gas to which thematerial is subjected for uniform drying.

10 Claims, 6 Drawing Figures PATENTEUmzs 1974 SL811 2.598

SHEU 1 or 2 APPARATUS FOR DRYING DAMP WEB MATERIAL The present inventionrelates to a device for drying a web of damp material, i.e. materialloaded with liquid or steam.

The problem of drying web material is met with frequently in industry,particularly in the textile industry, for example when it is necessaryto decrease the wetness ofa web of fabric leaving a dye bath or, moregenerally, an apparatus in which it has been subjected to treatment by aliquid or steam.

The same problem exists with strips or yarns, for example warped yarns,so the meaning of the word web in the following text should be definedat this stage. It refers to material which is in the form of a flexible,wide, longitudinally continuous sheet, or of an assembly oflongitudinally continuous, narrow strips arranged one beside the other,or of yarns, the width, i.e. the diameter, of which is very small andwhich are also positioned one beside the other.

Various processes and corresponding apparatus already exist for thepneumatic drying of a web of damp material moving continuously in itsown plane. Thus, for example, a table has already been used with whichthe web moves in contact, holes passing through the said table andforming a large number of orifices connected to a vacuum pump. As itpasses over these orifices, the liquid or steam contained in the web isaspirated, this reducing the wetness of the web.

However, such a process is not without disadvantages: in particular itsefficiency is very low because the depression is necessarily limited andthe energy consumed is badly utilised.

The process consisting of projecting a compressed gas onto the web ofdamp material is much more efficient and many types of nozzles designedfor this treatment have been described.

However, the use of jets of compressed air is not sufficient when theuniform drying of wide webs is required. The apparatus then become moreand more complex and less adaptable to the various types of products tobe treated.

The present invention is intended to overcome these disadvantages andproposes an efficient apparatus which adapts to the different productsto be treated and permits drying of products which are very wide and/orhave irregularities. The apparatus for drying a moving web of dampmaterial includes a distribution chamber through which the web to bedried passes and which is adapted to be maintained under pressure, thischamber having means for receiving a compressed gas, for examplecompressed air, from a calming chamber, and an input and an outputpassage for the web, each passage consisting of a slot. These slots areof a length of which is substantially equal to the width of the web tobe dired and preferably adjustable in order to enable the apparatus tobe adapted to the various products to be treated.

The apparatus can also have lateral slots and possibly particulardevices for controlling the width of the web.

When the web is very wide, the great width of the apparatus can causecertain elements to bend. Moreover, when the material hasirregularities, such as transversal extra thicknesses due for example toseams, auxiliary devices must be provided to correct these defects.

This is the object of a particular embodiment of the invention, in whichthe distribution chamber is defined by two elements, at least one ofwhich is deformable and is in equilibrium under the influence of on theone hand the pressure in the distribution chamber and on the other handof an auxiliary balancing force. This force is preferably acounter-pressure applied to the mobile element, for example from anauxiliary gas flow. This gas flow may be constant or otherwise andadjustable or otherwise, depending upon the required working conditions.Furthermore, the apparatus has means for varying the auxiliary balancingforce as a function of the pressure in the distribution chamber, forexample gasflow transfer channels. The apparatus also has means forlocally varying the pressure in the distribution chamber as a functionof the local conditions of the gas fed to the said distribution chamber.These means will, for example, be channels creating a charge lossbetween the feed chamber and the distribution chamber, the latter thenhaving a small cross-section.

A better understanding of the invention will be obtained from, andvarious secondary features and certain particular advantages will becomeapparent during the course of, the following description of someembodiments, with reference to the attached drawings in which:

FIG. 1 is a schematic, perspective view with a frontal section of anapparatus in accordance with the invention;

FIGS. 2 and 2a are detailed views showing two modifications of the formof the lips of the chamber slots;

FlG. 3 is a cross-section of the apparatus along the line lll [ll ofFIG. 1;

FIG. 4 is a partial section of FIG. 3 in the case of a modification;

FIG. 5 is a particular embodiment of the apparatus of FIG. 1.

If reference is made firstly to FIG. 1, it will be seen that theapparatus includes a lower table 1 on which the web to be dried 2 slidescontinuously. An elongate, hollow element, designated generally by 3, isarranged above web 2 and has at least one gas inlet 4, for example forcompressed air. The interior volume of hollow element 3 is preferablydivided into two chambers 7 and 8 by a partition 5 having judiciouslydistributed orifices 6. Chamber 7, known as the calming chamber,partition 5 and orifices 6 ensure suitable distribution of the gas inchamber 8, in such a way that the pressure prevailing in the latter isas uniform as possible.

lt is obvious that element 3 could be the lower element and element 1the upper element. Similarly, the lower and upper elements could beidentical to element 3, with two drying gas supplies.

Chamber 8, known as the distribution chamber, is defined by element 3itself and by table 1 and is thus traversed by the web to be dried 2.

Table l and element 3 are substantially equal in length to the width ofthe web to be dried. The input and output passages for the web consistof elongate slots 9a and 9b, the length of which is also substantiallyequal to thewidth of the web. The thickness of these slots isadjustable, so that the apparatus can easily be adapted to any productto be dried, whatever its thickness may be. Moreover, this facilitatesstarting of the equipment. In practice, this means that at least one ofelements 1 and 3, or only the lips of the slots, must be mobileperpendicularly tothe plane of the web to be dried. The means foreffecting this adjustment in .the thickness of the slots can be variousand are in any case very simple. It is not, therefore, necessary todescribe them here.

These slots can be closed at their lateral ends as shown in FIG. 4 orcan, on the contrary, be open, as is the case in the embodiment shown inFIG. 3. In this case they are extended along the lateral extremities ofhollow element 3 by slots extending in the direction of passage of theweb and between which the lateral margins of the web can move.

These lateral extremities can be used to control the thickness of theweb to be dried. As shown in FIG. 3, at least one detector 12 of theposition of the margin of the web relative to a fixed reference mark canbe provided. This detector, arranged adjacent to the transversealextremity of element 3, can be of any suitable type, for example opticalor mechanical. It is so constructed as to emit an output signal whichcontrols the adjustment of a valve 13 arranged in the gas supply 4. Thefeed pressure of the gas can thus be controlled into chamber 8 so thattransversal stretching of the web is constant.

The arrangement shown in FIG. 4 can also be used. In this case there areno slots at the ends of element 3; on the contrary, these extremitiesare closed and consist, either on table 1 or on element 3, of fullportions 14 forming the lateral walls of the distribution chamber anddefining guides for the lateral margins of the web. The distributionchamber then has a length slightly smaller than the width of the webto'be dried.

In the particular embodiment of this apparatus for the treatment ofirregular and/or very wide materials, shown in FIG. 5, element 3 whichincludes the dryinggas supply 4 is the lower element. The calmingchamber 7 is connected to distribution chamber 8 by conduits 6 playingapproximately the same role as the partition with orifices shown inFIG. 1. The dimensions of these conduits are so determined as to causethe appearance of charge losses in the drying-gas flow and theirdistribution is judiciously selected for there to be asubstantiallyuniform pressure in distribution chamber 8, which itselfhas a small cross-section. Upper element 22 is mobile between stops 27and 28 on the upper framework 29. It is made of any locally deformablematerial, for example a thin metal sheet. This element 22 is subjectedon its lower surface 30 to the action of the pressure prevailing indistribution chamber 8. For it to be in equilibrium, it is thereforenecessary to apply a secondary, auxiliary force to it. Inthe embodimentshown here, this force is a counter-pressure applied to this element 22.For this purpose, this element 22 has a deformable membrane 31 fixedtightly by any suitable means to a portion of its upper surface 32. Asthis membrane 31 is deformable, it is possible to form a chamber 33known as the equilibrium chamber between this membrane 31 and surface32. This chamber 33 communicates with distribution chamber 8 throughorifices 34, the purpose of which becomes apparent below and thedimensions, number and distribution of which are selected as a functionof the operating condition of the drying apparatus. Chamber 33, itselfdeformable, is fed with a stream of auxiliary gas, generally compressedair, the pressure and flow-rate of which are sufficiently low not tomodify the action of the drying gas on the material to be treated. Thesupply of auxiliary gas can be made at any point judiciously selectednot to impede the mobility of the lamina. The flow rate of thisauxiliary gas can be constant or otherwise, depending upon the operatingconditions. It can also be adjustable, for example as a function ofcertain parameters of the drying conditions.

It will be understood that it would be possible to use any other systemapplying a uniformly distributed auxiliary force to element 22 tomaintain it in equilibrium without departing from the scope of theinvention.

When element 22 is in equilibrium, the pressure inside equilibriumchamber 33 is then equal to the pressure on the lower surface 30 ofelement 22 plus the charge losses to which the auxiliary flow has beensubl5 ject in conduits 34. The pressure on lower surface 30,

depending essentially on the pressure prevailing in distribution chamber8, therefore depends upon two factors: the flow rate of the drying gasand the escape sec tion of this gas, i.e. in fact the distance d betweenelement 3 and mobile element 22. To each pressure in equilibrium chamber33 corresponds an equilibrium position of element 22, and a dryingpressure in distribution chamber 8. It is therefore possible to vary thedrying pressure in distribution chamber 8 and the equilibrium positionof element 22 by varying the equilibrium pressure in the equilibriumchamber. In the particular embodiment described here, it is sufficientfor that purpose to vary the flow rate of auxiliary gas, which is aparticularly simple means of adapting the apparatus described to anytype of material to be dried.

On the other hand, in addition to this possibility of adjusting the meandistance d between element 3 and mobile element 22, the apparatusdescribed here prevents local variation of d without however preventinggeneral variation in this same distance d. A local variation in dwouldbe caused, for example, by bending of the fixed'element, which bendingwill appear all the more rapidly as the apparatus is designed to treatvery wide materials. A local variation in d causes a local variation inthe flow-rate of the drying air. As the cross section of thedistribution chamber is small, there follows a local variation in thedrying pressure (by variation of the charge losses in conduits 6) andtherefore a local variation in the pressure on the lower surface 30 ofelement 22. The great flexibility of this element 22 enables it to bedeformed locally. It thus prevents local variation in d and remainssubstantially parallel at all points to element 3, whatever thedeformation of the latter may be. It acts to some extent as a correctorof local defects.

The above process is only possible because of the localisation ofvariations in the drying pressure, (localisation due to the smallcrosssection of the distribution chamber) in conjunction with uniformdistribution of the auxiliary balancing force, this distributionpermitting the appearance of local lacks of equilibrium and thus theconformation of the two elements.

On the contrary, this apparatus permits general and momentary variationin the distance d'made necessary in the case of generalised defects. Infact, materials having accidental extra thicknesses have often to betreated, in particular the connecting seams of pieces placed end to end.In this case, the distance d must increase and therefore element 22 movevery rapidly out of the way of a defect. However, this element 22 mustalso return to its equilibrium position immediately after passage of adefect to prevent the formation of wide, badly dried areas behind thisdefect. Conduits 34 which connect equilibrium chamber 33 anddistribution chamber 8 enable the pressure in each of them and,therefore, the pressures balancing mobile element 22 to be comparedconstantly. Thus they enable practically simultaneous variation of thetwo equilibrium pressures. When a general defect appears and causes ageneral variation in the pressure in distribution chamber 8, thisvariation is transmitted to the pressure in the equilibrium chamber andcauses displacement of mobile element 22. The reaction of the apparatusis small that is to say it is immediate and it disappears as soon as thedefect which has caused it disappears.

Similarly, it would be possible to make the lower element rather thanthe upper element mobile. All of the features could also be regrouped ona single element or a device could even be produced with two identicalelements, each of them having all of the features described. Theapparatus is selected according to the material to be treated and thetype of defects to be corrected.

The general operation of the apparatus as illustrated in FIGS. 1 to 5is, then, as follows.

With web 2 moving in the direction indicated by arrows A, inlet 4 isplaced in communication with a compressed-gas source. The gas flowsthrough orifices 6 to distribution chamber 8 and, because of thepresence of calming chamber 7, its pressure is substantially uniform inchamber 8. Acceleration of the gas is produced under the effect ofexpansion actually inside the web to be dried and not outside as happenswhen compressedair jets directed at the web are used. A first dryingaction is therefore obtained.

Furthermore, the gas escapes through slots 90 and 9b as well as, whereapplicable, through the end slots and this action completes drying. Thepressure at the inlet is controlled so as to obtain the best efficiency.In the zone of slots 9a and 9b mechanical wringing out of the liquidcontained in the web has been noted, favoured by the porosity of thelatter, which allows vibrations to appear. In fact the gas passesthrough the web (which, moreover, in the zone of the input slot travelsin the opposite direction to the gas current) so that the latter is notpermanently applied to the lower lip of the slot.

In addition, in the areas of the two slots, a depression zone is formeddue to the presence of the divergent resulting from the form of theslots; this favours evaporation of the liquid, or at least of the waterwhich it may contain.

These two effects are again reinforced by the presence of grooves orbaffles 11 in the lips of the slots which favour the appearance both ofvibrations and of localised depression zones. Moreover, the presence ofthese grooves decreases the mechanical friction of the web on the lips,thus facilitating its movement.

The apparatus also enables the width of the web to be controlled andthus facilitates its winding on a takeup roll or, more generally, itssubsequent use.

In the case of FIG. 3, an extension effect of the web controlled by thedetector 12 has been noted at the lateral extremities of chamber 8.

In the case of FIG. 4, the edges of chamber 8 directly gauge the web.

The large number of alternative constructions of this apparatus enableit to be adapted to any type of product to be treated.

What is claimed is:

1. Apparatus for pneumatically drying a web of porous damp materialmoving through said apparatus in a predetermined direction, saidapparatus comprising first and second frame elements, said first frameelement including means for providing a web engaging surface along whichthe web being dried moves during operation of the apparatus and saidsecond frame element including means cooperating with said web engagingsurface for forming an air distribution chamber in said apparatusthrough which said web moves, and an air supply chamber formed thereinin communication with said air distribution chamber for uniformlysupplying pressurized air from a source thereof to said distributionchamber; said frame elements being spaced from each other apredetermined distance to define therebetween inlet and outlet slots onopposite sides of said distribution chamber transversely to thedirection of movement of said web through the apparatus and throughwhich said web passes, said slots having a height dimension selected tobe substantially equal to the thickness of the web being treated,whereby pressurized air supplied to said distribution chamber is forcedinto the web to escape from said distribution chamber through saidslots, thereby to remove liquid from said web.

2. The apparatus as defined in claim 1 wherein said web engaging surfaceis substantially air-impervious whereby said pressurized air squeezessaid web in said distribution chamber forcing liquid out of the web andthrough said slots as the pressurized air escapes therefrom.

3. The apparatus as defined in claim I wherein said first and secondframe elements include substantially superimposed spaced wall portionsdefining said inlet and outlet slots, at least one of said wall portionshaving a plurality of grooves formed therein extending transversely ofthe direction of travel of said web whereby transversely extendingbaffles are defined in said at least one wall portion.

4. The apparatus as defined in claim 1 wherein said first and secondframe elements include opposed wall portions extending generallyparallel to the path of travel of said web through the apparatus and onopposite sides thereof, said opposed wall portions being spaced fromeach other to define auxiliary slots in said apparatus which receiveedge portions of said web and permit escape of part of the pressurizedair from said distribution chamber.

5. The apparatus as defined in claim 1 wherein said means providing saidweb engaging surface is mounted in said first frame element for movementwith respect to said second frame element in a direction generallyperpendicular to the plane of said surface, under the influence of thepressurized air in said distribution chamber; and means for producing anauxiliary balancing force for maintaining said web engaging surface in apredetermined balanced position with respect to said second frameelement.

6. The apparatus as defined in claim 5 wherein said means providing saidweb engaging surface is formed of a flexible material and is locallydeformable.

7. The apparatus as defined in claim 5 wherein said means for producingsaid auxiliary balancing force includes means for regulating said forceas a function of the pressure in the distribution chamber.

8. The apparatus as defined in claim wherein said first frame elementhas an auxiliary air chamber formed therein adapted to be connected to asource of pressurized air and located adjacent said means providing saidweb engaging surface, and on the opposite side thereof 5 from saidsurface, whereby the air pressure in said auxiliary chamber producessaid balancing force.

9. The apparatus as defined in claim 8 wherein said means providing saidweb engaging surface has a plurality of apertures therein providing aircommunication between said auxiliary chamber and said air distributionchamber whereby air in said auxiliary chamber escapes therefrom throughsaid apertures in accordance with the air pressure in said distributionchamber, thereby to vary the pressure in said auxiliary chamber and thebalancing foce produced thereby.

10. The apparatus as defined in claim 1 wherein said first frame elementhas an auxiliary air chamber formed therein opening towards said airdistribution chamber and said means providing said web engaging surfacecomprises a plate formed'of a flexible material movably mounted in saidfirst frame adjacent said auxiliary air chamber for movement towards andaway from said second frame element, said auxiliary air chamber beingoperatively connected to a source of air whereby an auxiliary balancingforce is produced on said plate for maintaining said web engagingsurface in a predetermined balanced position with respect to said airdistribution chamber-under the influence of the air pressure in said airdistribution chamber; said plate having a plurality of apertures thereinproviding air communication between said auxiliary chamber and said airdistribution chamber whereby air in said auxiliary chamber escapestherefrom through said apertures in accordance with the air pressure insaid distribution chamber, thereby to vary the pressure in saidauxiliary chamber and the balancing force produced thereby.

1. Apparatus for pneumatically drying a web of porous damp materialmoving through said apparatus in a predetermined direction, saidapparatus comprising first and second frame elements, said first frameelement including means for providing a web engaging surface along whichthe web being dried moves during operation of the apparatus and saidsecond frame element including means cooperating with said web engagingsurface for forming an air distribution chamber in said apparatusthrough which said web moves, and an air supply chamber formed thereinin communication with said air distribution chamber for uniformlysupplying pressurized air from a source thereof to said distributionchamber; said frame elements being spaced from each other apredetermined distance to define therebetween inlet and outlet slots onopposite sides of said distribution chamber transversely to thedirection of movement of said web through the apparatus and throughwhich said web passes, said slots having a height dimension selected tobe substantially equal to the thickness of the web being treated,whereby pressurized air supplied to said distribution chamber is forcedinto the web to escape from said distribution chamber through saidslots, thereby to remove liquid from said web.
 2. The apparatus asdefined in claim 1 wherein said web engaging surface is substantiallyair-impervious whereby said pressurized air squeezes said web in saiddistribution chamber forcing liquid out of the web and through saidslots as the pressurized air escapes therefrom.
 3. The apparatus asdefined in claim 1 wherein said first and second frame elements includesubstantially superimposed spaced wall pOrtions defining said inlet andoutlet slots, at least one of said wall portions having a plurality ofgrooves formed therein extending transversely of the direction of travelof said web whereby transversely extending baffles are defined in saidat least one wall portion.
 4. The apparatus as defined in claim 1wherein said first and second frame elements include opposed wallportions extending generally parallel to the path of travel of said webthrough the apparatus and on opposite sides thereof, said opposed wallportions being spaced from each other to define auxiliary slots in saidapparatus which receive edge portions of said web and permit escape ofpart of the pressurized air from said distribution chamber.
 5. Theapparatus as defined in claim 1 wherein said means providing said webengaging surface is mounted in said first frame element for movementwith respect to said second frame element in a direction generallyperpendicular to the plane of said surface, under the influence of thepressurized air in said distribution chamber; and means for producing anauxiliary balancing force for maintaining said web engaging surface in apredetermined balanced position with respect to said second frameelement.
 6. The apparatus as defined in claim 5 wherein said meansproviding said web engaging surface is formed of a flexible material andis locally deformable.
 7. The apparatus as defined in claim 5 whereinsaid means for producing said auxiliary balancing force includes meansfor regulating said force as a function of the pressure in thedistribution chamber.
 8. The apparatus as defined in claim 5 whereinsaid first frame element has an auxiliary air chamber formed thereinadapted to be connected to a source of pressurized air and locatedadjacent said means providing said web engaging surface, and on theopposite side thereof from said surface, whereby the air pressure insaid auxiliary chamber produces said balancing force.
 9. The apparatusas defined in claim 8 wherein said means providing said web engagingsurface has a plurality of apertures therein providing air communicationbetween said auxiliary chamber and said air distribution chamber wherebyair in said auxiliary chamber escapes therefrom through said aperturesin accordance with the air pressure in said distribution chamber,thereby to vary the pressure in said auxiliary chamber and the balancingfoce produced thereby.
 10. The apparatus as defined in claim 1 whereinsaid first frame element has an auxiliary air chamber formed thereinopening towards said air distribution chamber and said means providingsaid web engaging surface comprises a plate formed of a flexiblematerial movably mounted in said first frame adjacent said auxiliary airchamber for movement towards and away from said second frame element,said auxiliary air chamber being operatively connected to a source ofair whereby an auxiliary balancing force is produced on said plate formaintaining said web engaging surface in a predetermined balancedposition with respect to said air distribution chamber under theinfluence of the air pressure in said air distribution chamber; saidplate having a plurality of apertures therein providing aircommunication between said auxiliary chamber and said air distributionchamber whereby air in said auxiliary chamber escapes therefrom throughsaid apertures in accordance with the air pressure in said distributionchamber, thereby to vary the pressure in said auxiliary chamber and thebalancing force produced thereby.